Pharmacology of centrally acting analgesics: an introduction.

Aspirin-like drugs, paracetamol and amidopyrine exert their analgesic action predominantly at the site of origin of pain, e.g. in inflamed or functionally altered tissues. Opioids are thought to inhibit processing of pain-related neuronal inputs in the CNS including the spinal cord. This hypothesis has been extended by the discovery of opioid receptors, enkephalins and endorphins and interactions of these mediators with others including substance P, serotonin and other aminergic neurotransmitters. A review of the present situation is presented focussing on possible new sites of action of centrally acting analgesics.